最新刊期
卷 51 ， 期 2 ， 2012
- 摘要：Based on the numerical differential theory, it is available to calculate the approximate first derivative of the target-node by using numerical differentiation formulas when the discrete sampling points of the unknown target function on specified interval are given. But for the target-nodes close to the boundary, it may be unable to use the center differentiation formulas involving multiple nodes because of the lack of sampling points on one side of the target-node. Besides, an accelerating change of the first derivative of the target-node may occur in some target functions. However, the use of forward/backward differentiation formulas simply takes the nodes on one side of the target-node into consideration, which probably makes the formulas difficult to adapt to such a change, and thus leads to less accuracy in estimating the first derivative of the target-node. Actually, for the target-nodes close to the right boundary, it is available to move the backward differentiation formulas one node ahead to calculate the first derivatives. Therefore, one-node-ahead numerical differentiation formulas are proposed and investigated. Experimental results verify and show that the first derivatives of the target-nodes with high computational precision can be obtained by using the one-node-ahead numerical differentiation formulas.关键词：unknown target function;first derivatives;one node ahead;numerical differentiation formulas;computational precision
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发布时间：2023-12-11 - 摘要：Spectrum sensing-throughput tradeoff is investigated for a cognitive MIMO system. The objective is to find the optimal spectrum sensing time and optimal power allocation to maximize the throughput of secondary user. Simulation results show that there is indeed a unique optimal sensing time to make the throughput achieve the maximum. Further, the throughput of SU can be improved by using optimal power allocation. The throughput of SU with different spectrum sensing algorithms including energy detection and eigenvalue-based detection is compared by simulations. The results show that the eigenvaluebased detection is very appropriate for cognitive MIMO system, which is not only more robust than energy detection, but also satisfies the requirement of throughput.关键词：cognitive radio;optimal spectrum sensing time;throughput maximization;power allocation;tradeoff
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发布时间：2023-12-11 - 摘要：Stochastic vibration spectrum always contains sudden changes and discontinuance.On a wavelet denoising process, the soft-threshold method will make the estimation signal ambiguous at the discontinuity point, while the hard-threshold method will cause pseudo-Gibbs phenomena around the signal's discontinuity point. Through analysis on the statistic model of the stochastic vibration spectrum, a noise statistic model of numeric field vibration spectrum is established, and the nonlinear relationship between the filtering threshold-value and the wavelet transform scale is derived theoretically for providing a base for adaptive-threshold wavelet transform denoising. Finally,an universal adaptive denoising algorithm for vibration spectrum estimation based on wavelet transform is proposed. Simulation results show that the theoretical analysis is correct and the algorithm is good.关键词：vibration spectrum estimation;wavelet transform;nonlinear threshold
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发布时间：2023-12-11 - 摘要：Data, plan, model, knowledge and decisionmaking method for the storage and use as the core of public security data center is composed of storage devices, network equipment, application data and application integration.The data center has storage, query, management and maintenance functions. According to the demand of emergency platform, data center uses “ level + mixed ” method for architecture design. In the core layer, data, preplan, model, knowledge and decision-making method are mixed together according to the structure.The design of data center structure can realize data integration and management and provide effective access for a variety of application of emergency platform.关键词：data center;architecture;preplan base;model base;method base
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发布时间：2023-12-11 - 摘要：A spline smoothing method with natural boundary conditions for scattered data of 4D are considered. In order to minimization the given objective functional, using the spline function methods of Hilbert space, the solution is constructed as a piecewise trivariable polynomial. Its expression is so simple and the coefficients are decided by a linear system. Some numerical examples are presented to illustrate the method.关键词：scattered data;smoothing;natural boundary conditions;spline
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发布时间：2023-12-11 - 摘要：A mathematical model of the response of spatially structured tumors to chemotherapy: drug kinetics is studied. The model is a free boundary problem of a partial differential equation. The tumor is assumed to comprise a single cell population which reproduces and dies at a rate dependent on the local drug concentration. By using the method of the Lptheory for parabolic equations, the Banach fixed point theorem and the extensions method under some general conditions, it is proved that this problem has a unique global solution. And then, by applying upper and lower solution method in the theory of reaction diffusion equations under some other general conditions to obtain the stationary solution. It is proved that if 0关键词：tumor growth;free boundary problem;chemotherapy;global solution;stationary solution
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发布时间：2023-12-11 - 摘要：The quartic Hamilton system with quartic perturbed terms is studied. By using the accurate method to calculate the number of zeros of Abel integrals of the system, it is obtained that the system has at least 14 limit cycles.关键词：Hamilton system;limit cycle;Abel integrals
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发布时间：2023-12-11 - 摘要：It is an interesting and important problem to count the number of the perfect matchings in graphs, which origin from both physics and chemistry. So far, many mathematicians, physicists and chemists gave most of their attention to counting perfect matchings of graphs. But the problem of counting the number of the perfect matchings for general graphs is NP-difficult. By applying differentiation, summation and re-recursion calculation, the several counting formulas of the perfect matching for six specific types of graphs are given. As an application, the number of one type chessboard of the 1×2 dominoes covering is calculated.关键词：linear recurrence relation;chessboard;perfect matching
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发布时间：2023-12-11 - 摘要：The oscillation for a class of vector parabolic partial differential equations based on the influence of impulse and delay is investigated. By using impulsive delay differential inequality，some new sufficient criteria are established forH-oscillation of all solutions of such equations under Dirichlet boundary value condition， whereHis a unit vector in Rm. The obtained results fully reflect the influence action of impulse and delay in equation oscillation.关键词：oscillation;vector;parabolic equation;impulse;delay
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发布时间：2023-12-11 - 摘要：A nonlinear diffusive predator-prey model is studied under Dirichlet boundary conditions. Some a priori estimates are firstly derived. Then by investigating the corresponding eigenvalue problem and taking the growth rate of prey as a parameter, local bifurcation positive solutions emanating from the semitrivial solutions are obtained. Finally, by use of global bifurcation theory, two sufficient conditions for the existence of positive solutions are established.关键词：predator-prey;nonlinear diffusion;bifurcation
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发布时间：2023-12-11 - 摘要：β-Polypropylene (PP) blends were prepared with supported β-nucleator nucleated PP and PS, AS, ABS, respectively. The β-nucleation, crystallization behavior, melting characteristic and β-crystal content were investigated by DSC and WAXD. It was observed that the crystallization temperatures of β-nucleated PP slightly decreased with increasing styrenic polymers content, especially ABS. Addition of styrenic polymers had no influence on melting characteristic of β-nucleated PP， and three melting peaks were observed. Although the content of β-crystal in β-nucleated PP blends slightly decreased with increasing styrenic polymers content, β-PP blends were obtained with β-crystal content above 80%.关键词：β-polypropylene;styrenic polymers;crystallization and melting;crystlline morphology
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发布时间：2023-12-11 - 摘要：Research on the secondary metabolites of the mangrove endophytic fungusNigrosporasp. from the South China Sea was reported. Three secondary metabolites were isolated from the ethyl acetate extract of the fermentation by silica gel column chromatography, preparative thin layer chromatography and recrystallgraphy. Their structures were identified by comprehensive spectroscopic methods as Griseofulvin (1), Vermixocin B (2),Tenellic acid A(3). The absolute configuration of compound 1 was further confirmed by singlecrystal X-ray analysis. The cytotoxic activity of compound 1in vitro was also evaluated, and compound 1 showed medium activity against KB，KBV200，and A549 cell lines with IC50 of 8.23, 9.10 and 14.26 μmol/L, respectively.关键词：mangrove endophytic fungus;secondary metabolites;cytotoxic activity;X-ray diffraction
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发布时间：2023-12-11 - 摘要：Applyingo-nitrotoluent as starting material, 6-bromo-indole-3-carbinol was synthesized via multiple-step reactions including bromidation, aldollike condensation, cyclization, Vilsmeier-Haack formylation and reduction. The overall yield reaches 26.5%. The structures of all the products have been confirmed by ESI-MS and NMR. Based on the scaffold of the title compound, series of 6-substituted indole-3-carbinols can be prepared in search for the better drug-like compounds.关键词：indole-3-carbinol;anti-tumor;pharmaceutical synthesis
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发布时间：2023-12-11 - 摘要：Dihydroindazolocarbazoles(DHI-carbazoles) are the potent dual inhibitors to VEGFR2 and Tie-2. In this work, the mechanism of interaction between VEGFR2/Tie-2 and DHI-carbazoles was performed with Surflex-dock. The results from molecular docking indicated that DHI-carbazoles competitively bound to the active site, which was the substrate ATP in VEGFR2/Tie-2 with high affinity. The differences of activity between VEGFR2 and Tie-2 resulted from the minor difference of active pockets. Hydrophobic effect played a key role in the formation and stability. Hydrogen bond and electrostatic effect also contributed to the difference. This work elucidated the antitumor mechanism of the DHI-carbazoles as a dual potent inhibitor and provided theoretical basis for the design of tyrosine kinase inhibitors.关键词：molecular docking;tyrosine kinase inhibitors;VEGFR2;Tie-2
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发布时间：2023-12-11 - 摘要：hSSB1 is a key signaling moleculue that participates in DNA damage response. In this study, the cDNA ofhSSB1gene amplified by RT-PCR was inserted into the retroviral vector pBABE. The recombinant positive plasmid clone was identified by endonuclease digestion, PCR amplification and sequencing analysis. The retroviral expression vector pBABE-hSSB1and PIK packaging plasmid were cotransfected into 293T cells to produce the retrovirus. The packaging retrovirus was then infected into cancer cells and the overexpression cells were selected with puromycin. pBABE-hSSB1positive clones have been validated to be correct by restriction endonuclease, PCR amplification and DNA sequencing analysis. The protein level of hSSB1 in pBABE-hSSB1transfected cancer cell line was significantly up-regulated as validated by Western blotting. Our data indicate that the recombinant plasmid of pBABE-hSSB1was successfully constructed and transfected stably into cancer cells. It established a favorable foundation for further functional study.关键词：hSSB1;retroviral vector;stable cell line
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发布时间：2023-12-11 - 摘要：To explore the relationship between theIGF2bgene and growth traits, we cloned the introns ofIGF2bin common carp (Cyprinus carpio ) muscle and analysis its characters. Further more, the lentiviral vector(Lenti-IGF2-IRES-EGF) was constructed and its activity was also researched. The results showed that: the length of 5 173 bp DNA sequence of IGF2b(HM755899) was get, including 3 introns and 4 exons. Two CpG islands in the 3′untranslated region and (T)n repeat sequence in the 5′untranslated region were found. Besides these, the lentiviral vector(Lenti-IGF2b-IRES-EGF) was constructed successfully, which was cotransfected into 293T cells with the GFP expression. The higher expression of IGF2 was found in 293T cells by Real time PCR. These illustrated that these study may be lay on solid foundation for relationship betweenIGF2bgenetic diversity, expression and common carp growth traits.关键词：common carp;IGF2b;introns;lentiviral vector
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发布时间：2023-12-11 - 摘要：TheGTHα、LHβgene fragments were amplified by PCR,which the template was pituitary cDNA of marble eels. In the way of bridging，the two fragments were connected to a single geneLHβα,a linker inserted between them. The LHβαgene fragment was subcloned to pPICZαA with double enzyme digestion and connection, constructing eukaryotic coexpression plasmid pPICZα-LHβα. The recombinant plasmid was transfected into a native yeast strain X-33 by electrotransformation. The high-copy clones were selected by the YPDS plates containing different concentrations of Zeocin. The positive clones were induced by 0.7% methanol and expression products were tested by SDS-PAGE and western blot, and its molecular weight was determined as about 45 000.关键词：Anguilla marmorata;luteinizing hormone;linker;co-expression plasmid pPICZαA-LHβα;Pichia pastoris
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发布时间：2023-12-11 - 摘要：The experiment determined the metabolic rates of inorganic phosphorus, nitrite nitrogen, nitrate nitrogen and ammonia onM.japonicusunder different conditions. Results show that : temperature, weight, salinity, pH and feeding status effect metabolism. The metabolic rates of Phosphorus, nitrate nitrogen and ammonia nitrogen were negatively correlated with weight,but the metabolic rates of nitrite nitrogen decreased when weight increased. In the range of 20~30 ℃, as the temperature rose, the metabolic rates of phosphorus, nitrite nitrogen,nitrate nitrogen and ammonia increased. In the range of 10‰~31‰, as the salinity increased, the metabolic rates of phosphorus and nitrite nitrogen byM.japonicus(6.739±0.023) g increased, when the salinity is 31, the metabolic rates of phosphorus and nitrite nitrogen is (0.736±0.002) μg·g-1·h-1(0.0778±0.011) μg·g-1·h-1the metabolic rates of nitrate nitrogen, ammonia nitrogen decreased, when the salinity is 31, the metabolic rates of nitrate nitrogen, ammonia nitrogen is (0.257±0.207) μg·g-1·h-1(4.445±0.259) μg·g-1·h-1.In the range of 7.5~9.0, as the pH increased, the metabolic rates of phosphorus byMjaponicus(6.749±0.013) g decreased significantly. the metabolic rates of nitrate nitrogen and ammonia nitrogen increased. When pH was 8.5, the metabolic rates of nitrite nitrogen reached the maximum. Relative to the state of hunger, in the condition of feeding formula foodstuff, the metabolic rates of phosphate, nitrite nitrogen, nitrate nitrogen, ammonia nitrogen byMjaponicus(6.729±0.028) g, increased 272.02%,91.67%,795.38%,98.54%.关键词：Mjaponicus;nitrogen metabolism;phosphorus metabolism
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发布时间：2023-12-11 - 摘要：The morphology and regular pattern of prothoracic glands ofSpodoptera liturawere researched by dissecting these glands from the 4thinstar larvae to pupation. The result showed that the prothoracic glands ofS.liturawere in pair with Y-type, consisted of 53 round or oval cells, surrounded with transparent vaginal tunica, and located in the tracheal plexus of the first spiracle. The cells of prothoracic glands kept steady because of no mitosis from the 4thinstar larvae to pupation. The diameter of prothoracic gland cells was increased gradually during larval developments, the diameter of prothoracic gland cells from the larva at the first day of the 4th instar was (28.80±0.47) μm, while the diameter of prothoracic gland cells from the larva at the last day of 6 instar was (92.22±2.43) μm. There were significant relevance between the diameter of prothoracic gland cells and the weight of larva during the larval development, r=0.826, P=0.000, Y=82.1X0.263. There were also significant relevance between the diameter of prothoracic gland cells and the body length of larva during the larval development, r= 0.886, P=0.000, Y = e(4.781-1.863/Z).关键词：Spodoptera litura; prothoracic gland;development
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发布时间：2023-12-11 - 摘要：The comparison of the terrain data from the past 40 years shows that the inlet of the Xiaomiaohong channel has an evolutionary tendency of deposition in the north and erosion in the south. The north trough was silted constantly to disappear while the south trough developed adequately. The hydrodynamic mechanism of the change in deposition and erosion in different channels was discussed based on the analysis of field data and the tidal current Mathematical model. The reason that a state of deposition in the north and erosion in the south exists in the Xiaomiaohong channel during the past years is closely related to the tidal current characteristics in this area. The ebb flow discharge is stronger than flood in the south and middle waterways of the inlet, with an “ebb-dominated” style. On the contrary, the north waterway has a “flood-dominated” style. The sediment transportation shows a trend of northward inflow and southward outflow, consistent with the trend of deposition and atrophy in the north waterway and erosion and extension in the south waterway.关键词：radial sand ridges;Xiaomiaohong channel;tide channel;mathematic model
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发布时间：2023-12-11 - 摘要：Model identification of medium and longterm hydrologic forecast is studied in terms of pretreatment, data length and ways of modeling which are taken as primary factors for the prediction results. Based on finite sampling information criterion (FSIC), combined information criterion (CIC) is utilized to choose the proper order of the model. Kalman filtering is also used for nonlinear prediction. It is concluded that: 1) In model identification, reasonability of the pretreatment should be tested through the prediction results from the model if it significantly reduces the complexity of the model. 2) Data length of modeling should be long enough to reflect inherent oscillations of the time series while excessive amount brings in extra complexity, more time-consuming and less robustness. 3) Sliding model is better for larger flux and the streamflow peaks prediction, and sacrifices the precise of predicting relatively low run-off. 4) Kalman filtering used as a prediction method of runoff can remarkably raise the forecast effects in any sections of the range with the accuracy rate of peakprediction up to 63.64%.关键词：hydrologic forecast;model identification;CIC;Kalman filtering
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发布时间：2023-12-11 - 摘要：The LMS(Liuxihe Model) is a complete distributed physicsbased hydrological model,which is used to simulate and analyze the income flood of the Baipenzhu Reservoir in Guangdong province. The model is set up with DEM of precision of 200 m, landuse and soiltype of precision of 1 km. The basin is divided into five different watercourses which contain 48 virtual reaches according to crunodes set artificially,and then different reaches are given different initial parameters. Based on these given parameters,three floods and 11 floods are used to adjust and validate these initial parameters,respectively. The results indicate that parameters adjusted are of physical-base.The LMS model can simulate the income flood of the Baipenzhu Reservoir well and has extensive applicability and huge potential for floods simulation.关键词：floods simulation;distributed hydrological model;Liuxihe model;parameters adjustment;Baipenzhu Reservoir
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发布时间：2023-12-11 - 摘要：In order to study the influence of distribution of geochemical elements on mineralization, this study uses Q-Q plot and cluster analysis to discuss the space distribution of elements in Liujiashan of northern Guangdong province. 12 elements related to mineralization were analyzed on 1573 drainage sediment samples from Liujiashan to recognize their fractal distribution. In contrast to traditional anomaly recognition method with iterative mean ±σ, this paper uses C-A fractal to separate anomalies from their background values, and calculates multifractal spectrum function. The C-A fractal analysis unites element content and frequency distribution of statistic method and singularity space configuration. It is useful for distinguishing chemical background and anomalous values which are relate to mineralization, and can provide significant clue for mineral potential evaluation.关键词：geochemical;multifractal;C-A fractal analysis;anomalous values;Liujiashan of Northern Guangdong
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发布时间：2023-12-11 - 摘要：348 sediment samples were taken from the Pearl River Estuary to analyze their major element contents, and to study geochemical characteristics and geological significance. Results show that the main chemical compositions in surface sediments are SiO2and Al2O3with average contents up to 60.1% and 15.1% respectively. The content of SiO2increases from estuary to sea, while the content of Al2O3decreases. Correlation analysis and factor analysis show that SiO2Al2O3P2O5K2O, TiO2MnO, Fe2O3and CaO are the most important factors in surface sediments, mainly originated from continent and marine calcicolous livings. The elements originated from marine include Na2O and MgO, and K2O is derived from continent and marine.关键词：surface sediments;major element;geochemical characteristics;material sources;factor analysis;the Pearl River Estuary
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发布时间：2023-12-11 - 摘要：55 terraces along 32 rivers in eastern Guangdong and14C and TL ages from 25 samples are studied in this paper. There are at most 6 stages of river terraces in the region, of which the highest one is 70 m in height, and is distributed near present-day main riverbed. The first stage terraces include normality terraces (in the upper part of Lijui Town in Longchuan), semiburied terraces (from Lijui to Yuanzhou Town in Boluo), and buried terraces (from the downstream of Yuanzhou to the Dongjiang River Delta), with decreasing ages. This indicates that the tectonic lift occurred earlier or the lift rate was faster in the areas of river head and the tectonic activity was gradually stabilized or sunk in the areas of mid-downstream. There are at least 12 sites where typical denudeplanation surface gravel layers were found. They show the following characteristics: (1) They are distributed on the highest terraces with elevation of 20～200 m, coincident with local denudation platform. (2) They are located on terraces of the highest rank with large area in the region. (3) The denudeplanation surface gravel layers in Yulu of Shiyan Town, Pingling Town, Dongkeng Town, Shuichun Town, and Zhangfang Town are formed from former rivers. The valleys-in-valleys became today's little rivers with narrow riverbed and flood land, maybe with the first terraces, during the past hundreds of thousands years. (4) The denude-planation surfaces have two slope directions, towards the valley and the downstream in the basin, but generally towards the South China Sea.关键词：river terrace;denude-planation surface gravel layers;distribution;characteristics;eastern Guangdong
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发布时间：2023-12-11
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